Forming recesses in planar substrates has been carried out by etching processes, molding processes, and polishing methods using abrasive slurries.
U.S. Pat. Appl. Pub. No. 2012/0270016 A1 (Hashimoto et al.) describes a cover glass for use in a mobile device such as a touch-panel mobile telephone that has a recess that can be recognized as a character or a figure when watching from the front side of the mobile device or a recess that can be recognized when touching from the front side of the mobile device is formed on at least one of opposite main surfaces of the cover glass. A surface of this recess results from a chemical etching process. Such methods can involve hazardous chemicals, be difficult to control, and/or may alter the surface roughness or the chemical composition of the cover glass.
U.S. Pat. Appl. Pub. No. 2012/0287057 A1 (Wei) describes an integrated glass including a solid sculpted area with a number of concave shapes or convex shapes which can be used to form letters, numbers or patterns for user decorating or identifying. The shapes are formed by a process wherein a heated glass preform is pressed against a mold. This energy intensive process involves specialized equipment (e.g., an oven for heating the glass preform), and may not be well-suited for low volume or custom applications where mold fabrication costs may make it uneconomical.
Various dimpling grinders (e.g., a Model 200 Dimpling grinder marketed by E. A. Fischione Instruments, Inc.) have been commercially available. The devices are typically used for the preparation of high quality specimens for transmission electron microscopy (TEM) and as a test for evaluating the wear of coatings. The devices include a vertically oriented rotating wheel that contacts a horizontally rotating stage with the substrate mounted thereto. The wheel itself (which may be, for example, stainless steel, micarta, or wood) does not contain abrasive particles, but is used in combination with a slurry containing abrasive particles in a liquid vehicle. This process is relatively slow, messy, wasteful of abrasive particles, and can lead to distortions in the recess shape, poorer finish and lack of reproducibility.
There is a need for new methods and materials for creating recesses in substrates that overcome some or all of the above disadvantages.